| Influence of uniform momentum zones on frictional drag within the turbulent boundary layer |
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| 作者姓名： | 王康俊 姜楠 |
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| 作者单位： | Department of Mechanics;Tianjin Key Laboratory of Modern Engineering Mechanics |
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| 基金项目： | Project supported by the National Natural Science Foundation of China(Grant Nos.11732010,11972251,11872272,11902218,and 11802195);the National Key R&D Program of China(Grant No.2018YFC0705300). |
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| 摘 要： | Based on a set of experimental databases of turbulent boundary layers obtained from particle image velocimetry in the streamwise-wall-normal plane at friction-velocity-based Reynolds number Reτ=612,the influence of uniform momentum zones(UMZs)on the skin-friction drag is investigated.The skin-friction drag is measured by the single-pixel ensemble correlation method.The results show that the velocity fields with the number of UMZs larger than the mean value have a relatively low skin-friction drag,while the velocity fields with the number of UMZs less than the mean value have a relatively high skin-friction drag.By analyzing the statistical characteristics of UMZs,the dynamic correlation between the UMZs and skin-friction drag is explored.The velocity fields with a low number of UMZs present a sweep event.These sweep motions intensify the small-scale Reynolds shear stress in the near-wall region by modulation effects.The enhancement of small-scale Reynolds shear stress is the direct reason for the high skin-friction drag.Increasing the proportion of velocity fields with high UMZs amount may be a direction to reduce the skin-friction drag within the TBL.
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| 关 键 词： | turbulent boundary layers uniform momentum zones skin-friction drag |
Influence of uniform momentum zones on frictional drag within the turbulent boundary layer |
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| Kangjun Wang,Nan Jiang.Influence of uniform momentum zones on frictional drag within the turbulent boundary layer[J].Chinese Physics B,2021(3). |
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| Authors: | Kangjun Wang Nan Jiang |
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| Affiliation: | (Department of Mechanics,School of Mechanical Engineering,Tianjin University,Tianjin 300350,China;Tianjin Key Laboratory of Modern Engineering Mechanics,Tianjin 300072,China) |
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